The purpose of this study is to determine the effectiveness of audiovisual aids in the instruction of junior-level preservice teachers. The tapes used were vignettes of persons demonstrating specific teaching skills in the areas of lesson organization, questioning, using student ideas, praise and corrective feedback, and variety and variation in teaching styles. Ninety-six subjects were assigned to one of four groups. All groups were pretested and posttested with identical measures. For each of the five topics, the treatment groups were: tapes only; tapes plus instruction; instruction only; and control. It was hypothesized that preservice teachers who receive instruction and view protocol tapes will score significantly higher on related posttests than teachers who only receive instruction or who only view tapes. An unexpected consequence of this study was the finding that the control group, which received neither verbal nor visual instruction related to the topics of the tapes, performed just as well on related posttests as groups that did receive such instruction. The results of this study support the contention that no generalizations can be made concerning the effectiveness of media in instruction and that each type of media must be evaluated individually. (JD)